Open Source Ecosystems

=MapLayers plugin for Rails

MapLayers makes it easy to integrate a dynamic map in a Rails application. It can display map tiles and markers loaded from many different data sources. The included map viewer is OpenLayers[http://www.openlayers.org/]. With MapLayers you can display and publish ActiveRecord models with geographic data.

==Getting Started

Install the latest version of the plugin: ./script/plugin install git://github.com/pka/map_layers.git

Create a controller and a view ./script/generate controller Map index

===Initialization of the map Add the map viewer initialization to the index action in the controller: @map = MapLayers::Map.new("map") do |map, page| page << map.add_layer(MapLayers::GOOGLE) page << map.zoom_to_max_extent() end

Add this to the head of your view: <%= map_layers_includes :google => "ABQIAAAA3HdfrnxFAPWyY-aiJUxmqRTJQa0g3IQ9GZqIMmInSLzwtGDKaBQ0KYLwBEKSM7F9gCevcsIf6WPuIQ" %>

Put a map in the body your view:

<%= @map.to_html %>

Test your basic map with http://localhost:3000/map

===Multiple layers Add a second layer and some more controls in the controller action: @map = MapLayers::Map.new("map") do |map, page| page << map.add_layer(MapLayers::GOOGLE) page << map.add_layer(MapLayers::YAHOO_HYBRID)

page << map.add_control(Control::LayerSwitcher.new)
page << map.add_control(Control::Permalink.new('permalink'))
page << map.add_control(Control::MousePosition.new)

page << map.zoom_to_max_extent()

end

Add the Yahoo Javascript library to the includes: <%= map_layers_includes :google => "ABQIAAAA3HdfrnxFAPWyY-aiJUxmqRTJQa0g3IQ9GZqIMmInSLzwtGDKaBQ0KYLwBEKSM7F9gCevcsIf6WPuIQ", :yahoo => "euzuro-openlayers" %>

There are many more predefined layer types available: GOOGLE_SATELLITE, GOOGLE_HYBRID, GOOGLE_PHYSICAL, VE_ROAD, VE_AERIAL, VE_HYBRID, YAHOO, YAHOO_SATELLITE, YAHOO_HYBRID, MULTIMAP, OSM_MAPNIK, OSM_TELASCIENCE, GEOPOLE_OSM, NASA_GLOBAL_MOSAIC, BLUE_MARBLE_NG, WORLDWIND, WORLDWIND_URBAN, WORLDWIND_BATHY

To include all Javascript APIs, insert your API keys in the following statement: <%= map_layers_includes :google => "ABQIAAAA3HdfrnxFAPWyY-aiJUxmqRTJQa0g3IQ9GZqIMmInSLzwtGDKaBQ0KYLwBEKSM7F9gCevcsIf6WPuIQ", :multimap => "metacarta_04", :virtualearth => true, :yahoo => "euzuro-openlayers" %>

===Updating the map Now we want to add some simple markers in an Ajax action. First we add a link in the view:

<%= link_to_remote "Add marker", :url => { :action => "add_marker" } %>

This requires including the prototype library:

<%= javascript_include_tag 'prototype' %>

Then we include a marker layer in the map. Put this after the add_layer statements in the controller:

page.assign("markers", Layer::Markers.new('Markers')) page << map.addLayer(:markers)

and then we implement the Ajax action:

def add_marker render :update do |page| @markers = JsVar.new('markers') page << @markers.add_marker(OpenLayers::Marker.new(OpenLayers::LonLat.new(rand50,rand50))) end end

For accessing the marker layer in the Ajax action, we declare a Javascript variable with page.assign and access the variable later with the +JsVar+ wrapper.

===OpenStreetMap in WGS84

To overlay data in WGS84 projection you can use a customized Open Street Map:

@map = MapLayers::Map.new("map") do |map, page| page << map.add_layer(MapLayers::GEOPOLE_OSM) page << map.zoom_to_max_extent() end

=Publish your own data

Create a model: ./script/generate model --skip-timestamps --skip-fixture Place placeName:string countryCode:string postalCode:string lat:float lng:float rake db:migrate

Import some places: ./script/runner "Geonames::Postalcode.search('Sidney').each { |pc| Place.create(pc.attributes.slice('placeName', 'postalCode', 'countryCode', 'lat', 'lng')) }"

Add a new controller with a map_layer:

class PlacesController < ApplicationController

map_layer :place, :text => :placeName

end

And add a layer to the map:

page << map.addLayer(Layer::GeoRSS.new("GeoRSS", "/places/georss"))

Other types of served layers:

page << map.add_layer(Layer::GML.new("Places KML", "/places/kml", {:format=> JsExpr.new("OpenLayers.Format.KML")}))

page << map.add_layer(Layer::WFS.new("Places WFS", "/places/wfs", {:typename => "places"}, {:featureClass => JsExpr.new("OpenLayers.Feature.WFS")}))

==Spatial database support

Using a spatial database requires GeoRuby[http://georuby.rubyforge.org/] and the Spatial Adapter for Rails:

sudo gem install georuby ruby script/plugin install svn://rubyforge.org/var/svn/georuby/SpatialAdapter/trunk/spatial_adapter

Install spatial functions in your DB (e.g. Postgis 8.1): DB=map_layers_dev createlang plpgsql $DB psql -d $DB -q -f /usr/share/postgresql-8.1-postgis/lwpostgis.sql

Create a model: ./script/generate model --skip-timestamps --skip-fixture WeatherStation name:string geom:point rake db:migrate

Import some weather stations: ./script/runner "Geonames::Weather.weather(:north => 44.1, :south => -9.9, :east => -22.4, :west => 55.2).each { |st| WeatherStation.create(:name => st.stationName, :geom => Point.from_x_y(st.lng, st.lat)) }"

Add a new controller with a map_layer:

class WeatherStationsController < ApplicationController

map_layer :weather_stations, :geometry => :geom

end

And add a WFS layer to the map:

page << map.add_layer(Layer::WFS.new("Weather Stations", "/weather_stations/wfs", {:typename => "weather_stations"}, {:featureClass => JsExpr.new("OpenLayers.Feature.WFS")}))

==License The MapLayers plugin for Rails is released under the MIT license.

==Support For any questions, enhancement proposals, bug notifications or corrections visit http://rubyforge.org/projects/map-layers/ or send a mail to pka[at]sourcepole[dot]ch.